An encoder includes circuitry and memory coupled to the circuitry. In operation, the circuitry: encodes pictures in an encoding order according to temporal scalability that specifies temporal layers; adds, to a bitstream, information indicating whether CPB removal timings of lower pictures in one or more first temporal layers lower than or equal to a lower temporal layer lower than a higher temporal layer among the temporal layers in a first case in which the one or more first temporal layers are to be decoded are identical to CPB removal timings of the lower pictures in a second case in which second temporal layers lower than or equal to the higher temporal layer are to be decoded; and sets, in the information, a value indicating that the CPB removal timings in the first case are identical to the CPB removal timings in the second case.
Legal claims defining the scope of protection, as filed with the USPTO.
1. An encoder comprising: circuitry; and memory coupled to the circuitry, wherein in operation, the circuitry: encodes pictures in an encoding order according to temporal scalability that specifies temporal layers; and adds, to a bitstream, information indicating whether coded picture buffer (CPB) removal timings of lower pictures in one or more first temporal layers in a first case are identical to CPB removal timings of the lower pictures in a second case, the one or more first temporal layers being lower than or equal to a lower temporal layer lower than a higher temporal layer among the temporal layers, the first case being a case in which the one or more first temporal layers are to be decoded, the second case being a case in which second temporal layers lower than or equal to the higher temporal layer are to be decoded, one or more higher pictures in the higher temporal layer are placed between two adjacent lower pictures among the lower pictures in the encoding order, a total number of the one or more higher pictures placed between the two adjacent lower pictures is n−1, where n is an integer greater than 1 and denotes a ratio of a second frame rate in the second case to a first frame rate in the first case, and when the n is not equal to 2, the information indicates that the CPB removal timings of the lower pictures in the first case are not identical to the CPB removal timings of the lower pictures in the second case.
2. The encoder according to claim 1, wherein the n is equal to 2, and higher pictures in the higher temporal layer and the lower pictures are alternately arranged in the encoding order.
3. The encoder according to claim 1, wherein the n is equal to 4, the lower pictures are arranged m-th in the encoding order, m being an integer greater than or equal to 0, and higher pictures to be encoded only in the second case are arranged (m+1)-th, (m+2)-th, and (m+3)-th in the encoding order.
4. The encoder according to claim 1, wherein the pictures include second pictures, the second pictures being included in (i) one or more third temporal layers lower than or equal to a temporal layer other than the lower temporal layer and the higher temporal layer, (ii) in one or more first temporal layers, and (iii) in the second temporal layers, the information indicates that CPB removal timings of the second pictures in the first case are identical to CPB removal timings of the second pictures in the second case, and the circuitry adds, to the bitstream, second information indicating whether the CPB removal timings of the second pictures in the first case or the second case are identical to CPB removal timings of the second pictures in a third case in which the one or more third temporal layers are to be decoded.
5. The encoder according to claim 4, wherein the one or more third temporal layers are one or more second lower temporal layers lower than the lower temporal layer, and the circuitry: adds, to the bitstream, the information indicating that the CPB removal timings of the second pictures in the first case are identical to the CPB removal timings of the second pictures in the second case; and adds, to the bitstream, the second information indicating that the CPB removal timings of the second pictures in the first case or the second case are not identical to the CPB removal timings of the second pictures in the third case.
6. The encoder according to claim 1, wherein the information includes: first delay information indicating whether a first delay of a CPB removal timing of the higher temporal layer relative to a CPB removal timing of a highest temporal layer is present; and second delay information indicating whether a second delay of a CPB removal timing of the lower temporal layer relative to the CPB removal timing of the highest temporal layer is present.
7. The encoder according to claim 6, wherein when the higher temporal layer is the same as the highest temporal layer, the information does not include the first delay information, and when the higher temporal layer is not the same as the highest temporal layer, the information includes the first delay information.
8. A decoder comprising: circuitry; and memory coupled to the circuitry, wherein in operation, the circuitry: obtains, from a bitstream, information indicating whether coded picture buffer (CPB) removal timings of lower pictures in one or more first temporal layers in a first case are identical to CPB removal timings of the lower pictures in a second case, the one or more first temporal layers being lower than or equal to a lower temporal layer lower than a higher temporal layer among the temporal layers, the first case being a case in which the one or more first temporal layers are to be decoded, the second case being a case in which second temporal layers lower than or equal to the higher temporal layer are to be decoded; and decodes, based on the information, pictures in a decoding order according to temporal scalability that specifies temporal layers, one or more higher pictures in the higher temporal layer are placed between two adjacent lower pictures among the lower pictures in the decoding order, a total number of the one or more higher pictures placed between the two adjacent lower pictures is n−1, where n is an integer greater than 1 and denotes a ratio of a second frame rate in the second case to a first frame rate in the first case, and when the n is not equal to 2, the information indicates that the CPB removal timings of the lower pictures in the first case are not identical to the CPB removal timings of the lower pictures in the second case.
9. The decoder according to claim 8, wherein the n is equal to 2, and higher pictures in the higher temporal layer and the lower pictures are alternately arranged in the decoding order.
10. The decoder according to claim 8, wherein the n is equal to 4, the lower pictures are arranged m-th in the decoding order, m being an integer greater than or equal to 0, and higher pictures to be decoded only in the second case are arranged (m+1)-th, (m+2)-th, and (m+3)-th in the decoding order.
11. The decoder according to claim 8, wherein the pictures include second pictures, the second pictures being included in (i) one or more third temporal layers lower than or equal to a temporal layer other than the lower temporal layer and the higher temporal layer, (ii) in one or more first temporal layers, and (iii) in the second temporal layers, the information indicates that CPB removal timings of the second pictures in the first case are identical to CPB removal timings of the second pictures in the second case, and the circuitry adds, to the bitstream, second information indicating whether the CPB removal timings of the second pictures in the first case or the second case are identical to CPB removal timings of the second pictures in a third case in which the one or more third temporal layers are to be decoded.
12. The decoder according to claim 11, wherein the one or more third temporal layers are one or more second lower temporal layers lower than the lower temporal layer, and the circuitry: adds, to the bitstream, the information indicating that the CPB removal timings of the second pictures in the first case are identical to the CPB removal timings of the second pictures in the second case; and adds, to the bitstream, the second information indicating that the CPB removal timings of the second pictures in the first case or the second case are not identical to the CPB removal timings of the second pictures in the third case.
13. The decoder according to claim 8, wherein the information includes: first delay information indicating whether a first delay of a CPB removal timing of the higher temporal layer relative to a CPB removal timing of a highest temporal layer is present; and second delay information indicating whether a second delay of a CPB removal timing of the lower temporal layer relative to the CPB removal timing of the highest temporal layer is present.
14. The decoder according to claim 13, wherein when the higher temporal layer is the same as the highest temporal layer, the information does not include the first delay information, and when the higher temporal layer is not the same as the highest temporal layer, the information includes the first delay information.
15. An encoding method comprising: encoding pictures in an encoding order according to temporal scalability that specifies temporal layers; and adding, to a bitstream, information indicating whether coded picture buffer (CPB) removal timings of lower pictures in one or more first temporal layers in a first case are identical to CPB removal timings of the lower pictures in a second case, the one or more first temporal layers being lower than or equal to a lower temporal layer lower than a higher temporal layer among the temporal layers, the first case being a case in which the one or more first temporal layers are to be decoded, the second case being a case in which second temporal layers lower than or equal to the higher temporal layer are to be decoded, wherein one or more higher pictures in the higher temporal layer are placed between two adjacent lower pictures among the lower pictures in the encoding order, a total number of the one or more higher pictures placed between the two adjacent lower pictures is n−1, where n is an integer greater than 1 and denotes a ratio of a second frame rate in the second case to a first frame rate in the first case, and when the n is not equal to 2, the information indicates that the CPB removal timings of the lower pictures in the first case are not identical to the CPB removal timings of the lower pictures in the second case.
16. A decoding method comprising: obtaining, from a bitstream, information indicating whether coded picture buffer (CPB) removal timings of lower pictures in one or more first temporal layers in a first case are identical to CPB removal timings of the lower pictures in a second case, the one or more first temporal layers being lower than or equal to a lower temporal layer lower than a higher temporal layer among the temporal layers, the first case being a case in which the one or more first temporal layers are to be decoded, the second case being a case in which second temporal layers lower than or equal to the higher temporal layer are to be decoded; and decoding, based on the information, pictures in a decoding order according to temporal scalability that specifies temporal layers, wherein one or more higher pictures in the higher temporal layer are placed between two adjacent lower pictures among the lower pictures in the decoding order, a total number of the one or more higher pictures placed between the two adjacent lower pictures is n−1, where n is an integer greater than 1 and denotes a ratio of a second frame rate in the second case to a first frame rate in the first case, and when the n is not equal to 2, the information indicates that the CPB removal timings of the lower pictures in the first case are not identical to the CPB removal timings of the lower pictures in the second case.
17. A non-transitory medium storing a bitstream, the bitstream including instructions causing a decoder to perform a decoding process, the decoder receiving the bitstream, wherein the bitstream includes information for decoding pictures in the decoding process in a decoding order according to temporal scalability that specifies temporal layers, the information indicates whether coded picture buffer (CPB) removal timings of lower pictures in one or more first temporal layers in a first case are identical to CPB removal timings of the lower pictures in a second case, the one or more first temporal layers being lower than or equal to a lower temporal layer lower than a higher temporal layer among the temporal layers, the first case being a case in which the one or more first temporal layers are to be decoded, the second case being a case in which second temporal layers lower than or equal to the higher temporal layer are to be decoded, and when n is not equal to 2, the information indicates that the CPB removal timings of the lower pictures in the first case are not identical to the CPB removal timings of the lower pictures in the second case, the n being an integer greater than 1 and denoting a ratio of a second frame rate in the second case to a first frame rate in the first case.
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December 9, 2022
February 18, 2025
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